A common task in the manipulation of digital images is the removal of one or more foreground objects from a scene and the composition of this object with a new background image. This is typically a difficult task for several reasons:
1) blending of an object with the background scene: a pixel at an edge of an object may have contributions from both the foreground and the background, its color is consequently a blend of the two regions;
2) object complexity: even for objects with hard edges, the object border often contains detail that requires tedious effort to define manually; and
3) combinations of 1) and 2): an example is hair or fur, the shapes are complex and regions with thin fibers lead to color blending.
In general, the problem does not have a simple unambiguous solution. The movie industry has handled this by simplifying the scene, by filming objects or people against a simple background (blue screen) having as uniform a color as possible. Techniques have been developed to produce approximate solutions in this situation. Software products that can be used to mask an object, require a great deal of manual effort for complex objects such as subjects with hair. Existing products also enable a degree of color extraction from simplified background scenes by applying operations to the color channels.